I've voted none, though I may very rarely watch an English or European game, but otherwise have watched nothing but Rangers for a good few years.
May be partly an age thing (I'm now 61). As a boy there was very little live football shown on TV, mainly just major cup finals & internationals, so at that time we had to rely on 2 weekend & infrequent midweek highlights shows, but I would watch anything & everything I could. I could have named the first teams of probably every Scottish & English 1st division clubs, knew cup winners north & south of the border from the war onwards, European & World Cup too. Probably still can up to the mid 1990's, but would struggle to tell you who won trophies in last 10 years.
Interest in general football probably ended about 20 years ago, went to virtually all our away games until around 2005, but hardly been since. Our ridiculous league set up with the uneven 'split', Nationalist takeover of our national teams support, & the response of the SFA & other clubs in 2012 have all contributed, but career & family also tends to influence the interest level over time.
Might be just a boring old fart now, but football seemed so much more enjoyable 30 plus years ago. For me it's Ibrox season ticket & pub for away games now. Too much commercial domination of the game, focus on the 'big' leagues & Champions League. As for behind closed door games - pointless.
Doubt if I'm alone in this view & would be interested to know if many other posters from my age group have the same level of interest as they would have had a schoolboy.